[nilez]

It's not so much about aerodynamics that saves you gas. It has to do with how hard the engine is working to maintain a given speed and how far of a distance you can travel at that speed. On my old Honda Accord, there was a yellow 55 mph mark (all the rest of the ticks were 10, 20, 30, 40, 50 etc written in white). The purpose of the yellow 55 mph was to indicate that that particular vehicle got the best gas mileage at 55 mph. So if you're comparing 65 mph to 75 mph, at 75 mph you're going faster and will reach your destination quicker (less time the car is on), but your engine is also working much harder (higher rpm's = burning more gas) than it would be at 65 mph.

As for the lowering the speed limits... I'm pretty sure that's ridiculous. If they wanna help the public out with high gas prices, lower the damn prices on gas! not the freakin speed limits... buncha arseholes.